apple states that the biggest reason why they didn't include a charging adapter for the iPhone 12 was because of environmental reasons. So my question is, Wouldn't it create more emissions for me to to order a charging adapter that is packaged and shipped separately?
No, if this is your first smartphone ever you just buy a power adapter, say the new Nano one from Anker and use it instead so you can have fast charging (this move also helps other manufacturers). Or, if you have old power adapters I'm sure you have older cables, just use them.
Please see the following extract:
As part of our efforts to reach our environmental goals, iPhone 13 and iPhone 13 mini do not include a power adapter or EarPods. Included in the box is a USB‑C to Lightning Cable that supports fast charging and is compatible with USB‑C power adapters and computer ports.
We encourage you to re‑use your current USB‑A to Lightning cables, power adapters, and headphones, which are compatible with these iPhone models. But if you need any new Apple power adapters or headphones, they are available for purchase.
This is from https://www.apple.com/shop/buy-iphone/iphone-13
I hope that explains everything for you, please be advised that you are able to purchase a new charging adapter if you require it from the Apple Online Store, however you are able to use your old charging cable and adapter from a previous iPhone if you have one with USB to lightning capabilities.
Charging adapter
